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Jim Blackwood's 1971 MGB with supercharged/turbocharged Oldsmobile 215 V8

Jim Blackwood · 1971 MGB

MG MGB

BritishV8: the site for enthusiasts of modified British sports carsBritish V8 Newsletter, Volume 6 Issue 2, August 1998

Read the full write-up at BritishV8: the site for enthusiasts of modified British sports cars ↗

Photo: BritishV8: the site for enthusiasts of modified British sports cars

A 1971 MGB rebuilt with a turbocharged, then supercharged, Oldsmobile 215 V8

Jim Blackwood swapped his 1971 MGB's engine for a 1963 Oldsmobile 215 V8, first fitted with the factory turbocharger and later converted to supercharged EFI with home-built induction and controls. The write-up covers his self-fabricated headers, custom cooling and brake-bias systems, and extensive trim and chassis modifications, making it a detailed record of a long-running, heavily hand-built conversion.

Specs

As stated in the original write-up.

Engine
1963 Oldsmobile 215 V8 from a F-85, extensively modified, originally with Olds factory turbocharger, later converted to supercharged EFI
Supercharger
Eaton M90 (Generation 4)
Fuel/Ignition
Enderle-style custom triple throttle body EFI with MegaSquirt control; previously Ford EEC-IV SEFI mass-air system with TwEEcer control
Transmission
Late 1970s Borg Warner T-50 (Monza) close-ratio gearbox with road-race shift pattern
Bellhousing
D&D Fabrications, offset dowel pins for crank-to-transmission alignment
Clutch
10-1/2 inch diaphragm clutch (NAPA, for GM)
Flywheel
D&D Fabrications lightweight flywheel
Exhaust
Owner-fabricated 8-into-4-into-1 heavy wall turbo headers, 2 inch exhaust, no muffler or catalytic converter
Brakes
1975 Mach 1 Mustang ventilated rotors and calipers front, stock drums rear, dual master cylinders with dash-adjustable balance bar
Wheels/Tyres
Centerline wheels, standard offset, Goodrich 265/50/14 tyres on 7 inch wheels, custom front and rear hubs
Suspension
Huffaker front springs, lowered 1 inch de-arched rear springs with one added leaf, competition valved shocks with light oil, Delrin A-arm bushings, GT front sway bar, near-zero toe-in
Cooling
Custom 5-core radiator 4 inches longer than stock, relocated filler, steel flex fan on crankshaft, pressurized overflow tank, coolant line to turbo compressor housing
Rear axle
Stock MGB axle with flanges replaced for 5-lug, 4-1/2 inch bolt circle (small Ford pattern)
Interior
Leather Mercury Marauder seat backs grafted to MGB bases, handcrafted wooden door trim, wooden brake bias knob
Aerodynamics
Oldsmobile 442 rear wing with trim linkage that automatically reduces drag at speed

Parts used

Parts named as used in the original write-up, grouped the way the Parts page groups them. Where one of the shops we index lists the same thing for this car, it is shown underneath with a link to the shop.

Engine 2

Fuel & Ignition 8

Cooling 4

Gearbox & Drivetrain 6

Suspension & Steering 5

Brakes 2

Wheels & Tyres 3

  • Centerline wheelsCenterline

    Standard offset wheels fitted with custom hubs

  • Goodrich 265/50/14 tyresBF Goodrich

    Fitted on 7 inch wide wheels

  • Custom front and rear hubs

    Built to adapt wheels and bearings to the V8 swap

Body & Trim 3

  • Modified hood

    Reworked with forward tilt and splice to clear the supercharger

  • Hidden bumper splice

    Concealed under the over-rider for body modification

  • Oldsmobile 442 rear wingOldsmobile

    Provides cornering downforce, with trim linkage reducing drag at speed

Interior 3

Electrical 2

Photos

37 pictures collected from the write-up, in the order they were posted, shown from BritishV8: the site for enthusiasts of modified British sports cars. A picture opens larger here, with the way through to the page it is on.

Jim Blackwood's wicked blown Oldsmobile 215cid powered MGBPhoto: BritishV8: the site for enthusiasts of modified British sports cars
Oldsmobile 215 valve coverPhoto: BritishV8: the site for enthusiasts of modified British sports cars
K&N filter for crankcase ventPhoto: BritishV8: the site for enthusiasts of modified British sports cars
custom triple throttle bodyPhoto: BritishV8: the site for enthusiasts of modified British sports cars
throttle linkagePhoto: BritishV8: the site for enthusiasts of modified British sports cars
throttle position sensorPhoto: BritishV8: the site for enthusiasts of modified British sports cars
ethanol vapor intercoolerPhoto: BritishV8: the site for enthusiasts of modified British sports cars
home-made plenumPhoto: BritishV8: the site for enthusiasts of modified British sports cars
sneeze valvePhoto: BritishV8: the site for enthusiasts of modified British sports cars
cam position sensorPhoto: BritishV8: the site for enthusiasts of modified British sports cars
custom radiator and fan shroudPhoto: BritishV8: the site for enthusiasts of modified British sports cars
surge tankPhoto: BritishV8: the site for enthusiasts of modified British sports cars
custom headers and fender vent fanPhoto: BritishV8: the site for enthusiasts of modified British sports cars
wiring, relays, and circuit protectionPhoto: BritishV8: the site for enthusiasts of modified British sports cars
Eaton M90 (Generation 4) SuperchargerPhoto: BritishV8: the site for enthusiasts of modified British sports cars
fog lights and modified ST spoilerPhoto: BritishV8: the site for enthusiasts of modified British sports cars
cold air intake ductworkPhoto: BritishV8: the site for enthusiasts of modified British sports cars
throttle body and mass air flow (MAF) sensorPhoto: BritishV8: the site for enthusiasts of modified British sports cars
mass flow sensorPhoto: BritishV8: the site for enthusiasts of modified British sports cars
Rover fuel railPhoto: BritishV8: the site for enthusiasts of modified British sports cars
hood weldingPhoto: BritishV8: the site for enthusiasts of modified British sports cars
supercharger thru hoodPhoto: BritishV8: the site for enthusiasts of modified British sports cars
forward tilt hoodPhoto: BritishV8: the site for enthusiasts of modified British sports cars
fitting of hoodPhoto: BritishV8: the site for enthusiasts of modified British sports cars
bumper splice hidden under over-riderPhoto: BritishV8: the site for enthusiasts of modified British sports cars
double hingePhoto: BritishV8: the site for enthusiasts of modified British sports cars
mechanically adjustable brake bias mechanismPhoto: BritishV8: the site for enthusiasts of modified British sports cars
pedal hangs between master cylinders, pivoting on a spherical bearing on a threaded rodPhoto: BritishV8: the site for enthusiasts of modified British sports cars
side-to-side location of the pivot point determines relative piston travel and thus brake biasPhoto: BritishV8: the site for enthusiasts of modified British sports cars
brake bias adjustment knobPhoto: BritishV8: the site for enthusiasts of modified British sports cars
handcrafted wooden door trimPhoto: BritishV8: the site for enthusiasts of modified British sports cars
Mercury Marauder seatsPhoto: BritishV8: the site for enthusiasts of modified British sports cars
MGB door panel and map pocketPhoto: BritishV8: the site for enthusiasts of modified British sports cars
Oldmobile 442 wingPhoto: BritishV8: the site for enthusiasts of modified British sports cars
trim linkage (to reduce drag at speed)Photo: BritishV8: the site for enthusiasts of modified British sports cars
Jim Blackwood of Blackwood LabsPhoto: BritishV8: the site for enthusiasts of modified British sports cars
InventorsPhoto: BritishV8: the site for enthusiasts of modified British sports cars

How it was done

Choosing the engine

Jim started with a 1963 Oldsmobile 215 V8 from an F-85, modifying it extensively and pairing it with the engine's original factory turbocharger as the first power setup for his MGB.

Drivetrain fabrication

He fitted a close-ratio Borg Warner T-50 gearbox, reshaping its shifter and adding a custom walnut handle. D&D Fabrications supplied a bellhousing with corrected dowel alignment and a lightweight flywheel, while a NAPA diaphragm clutch and slave cylinder completed the package, though the slave required an awkward footwell box.

Exhaust and cooling

Jim hand-built heavy wall turbo headers in an 8-into-4-into-1 configuration, running straight pipe with no muffler or catalytic converter. He also built a custom 5-core radiator, longer than stock, with a relocated filler neck, pressurized overflow tank, and a coolant line feeding the turbo's compressor housing.

Chassis and brakes

Suspension was reworked with Huffaker front springs, de-arched and re-leafed rear springs, competition shock valving, Delrin bushings, and a GT sway bar. Braking came from Mustang Mach 1 front rotors and calipers with stock rear drums, controlled through a dual master cylinder setup with a dash-adjustable balance bar for brake bias.

Wheels and rear end

Centerline wheels were fitted with Goodrich tyres over custom front and rear hubs, and the stock MGB rear axle was adapted with 5-lug flanges to a small Ford bolt pattern.

Switch to supercharged EFI

The car was later updated from its original Ford mass-air EFI system to a supercharged setup using an Eaton M90 Generation 4 supercharger, a custom triple throttle body, home-fabricated brass plenum, ethanol vapor intercooler, and MegaSquirt engine control.

Body and interior details

Bodywork included a hood modification to clear the supercharger, a hidden bumper splice, and an Oldsmobile 442 wing with linkage that reduces drag at speed. Inside, Mercury Marauder leather seats were grafted onto MGB bases and the door trim was handcrafted in wood.

A summary in our own words. The full account, with all its detail, is in the original write-up: read it at BritishV8: the site for enthusiasts of modified British sports cars ↗

Worth knowing

  • The close-ratio Borg Warner T-50 gearbox is a better choice than the wide-ratio version.
  • Use a hydraulic throw-out bearing setup rather than the clutch slave arrangement used here, which required an awkward footwell box.
  • Learning to gas weld to make your own headers is worthwhile and not as difficult as expected.
  • It is possible to retain the stock starter by rotating its nose, using an available aluminum starter nose.
  • A Geo Metro alternator is small, effective, and easy to mount in a V8 swap.

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